The present invention relates generally to a lightfast epoxy resin formed from phosgenated Bisphenol A which is employed as a sunlight resistant vehicle paint or coating.
The sheet metal of a vehicle is usually coated with paint to enhance vehicle appearance and to provide corrosion protection. The paint is composed of powder mixed with an epoxy resin. The epoxy resin is commonly formed by the reaction of Bisphenol A and epichlorohydrin. Epichlorohydrin includes an oxirane ring, which is known as the epoxy group. Bisphenol A contains benzene rings. As with most chemicals with benzene rings, Bisphenol A absorbs actinic ultraviolet light in the range of 280 to 310 nm and is therefore not lightfast and not durable to ultraviolet light. Therefore, the prior art paints employing an epoxy resin composed of Bisphenol A and epichlorohydrin tend to chalk outdoors when exposed to sunlight. To increase gloss retention and reduce fading, paint is usually applied to the vehicle in two coats. As epichlorohydrin is transparent to sunlight, the lack of sunlight resistance is due to the Bisphenol A. In the prior art, resins including phosgenated Bisphenol A have been used as a photoresist for printing.
Polycarbonate is a polymer which contains phosgenated Bisphenol A and is resistant to sunlight. Polycarbonate is lightfast because the Bisphenol A is phosgenated. When exposed to sunlight, the phosgene of the polycarbonate undergoes a Photo-Fries rearrangement to form alpha hydroxy benzophenone, the ingredient found in suntan location. The alpha hydroxy benzophenone is stabilized by a mechanism called phototaumerism. Due to phosgenation of the Bisphenol A in polycarbonate, the properties of polycarbonate change slowly during ultraviolet irradiation. Although polycarbonate resins are sunlight resistant, polycarbonate is not used in coatings because of its large molecule size and high molecular weight.
This invention relates to a method of forming a lightfast epoxy resin which can be used as a sunlight resistant paint or coating on a vehicle. Bisphenol A is phosgenated by a reaction with phosgene to produce Bisphenol A bischloroformate, which includes a phosgene moiety on each end.
The Bisphenol A bischloroformate is then reacted with another chemical to produce a lightfast epoxy resin. The chemical can be epichlorohydrin, glycidol, or pinacol. If the Bisphenol A bischloroformate is reacted with either epichlorohydrin or glycidol, an epoxy resin is produced. The Bisphenol A bischloroformate can also be reacted with pinacol to produce a building block which can be reacted with epichlorohydrin or glycidol to produce an epoxy resin having an increased viscosity.
When exposed to ultraviolet light, the phosgene moiety in the epoxy resin undergoes a Photo-Fries rearrangement to form an alpha hydroxy benzophenone, the ingredient found in suntan lotion. Alpha hydroxy benzophenone is stabilized by a mechanism called phototaumerism. In phototaumerism, the hydrogen of the hydroxy group wiggles and dissipates heat as energy, stabilizing the alpha hydroxy benzophenone and reducing degradation by sunlight.
By phosgenating the Bisphenol A prior to the reaction with an additional chemical, the resulting epoxy resin has improved lightfastness and is not degraded by sunlight. The epoxy resin of the present invention can be used in paints, coatings, and plastics on vehicles, such as boats, cars and planes.